1. Field of the Invention
This invention relates to a method of manufacturing drive plates for use in drive gears of clutches for motor vehicles.
2. Description of the Prior Art
Large sized drive plates each of which diameter is 200 mm or more have been manufactured by the steps of press-fitting a dish-shaped member formed by pressing a disc-shaped thin plate material into an annular gear member having gear teeth formed along the outer periphery of an annular raw material, and fixedly securing both the component parts by welding.
Further, besides the above-mentioned method of manufacturing a drive plate, there are methods of manufacturing a drive plate comprising the steps of forming an outer peripheral portion of a disk-shaped thin plate material in a thick peripheral wall by folding as disclosed in Japanese Patent Publications Nos. SHO 54-44259 and SHO 54-20190 or spinning that portion as disclosed in West German Patent No. 38 19 957, and then forming gear teeth at the thick-walled peripheral portion.
Out of the above-mentioned prior art methods, in the former method of manufacturing a drive plate from the two component parts, since the gear teeth of a gear member are formed by machining using a gear hobbing machine, the cost of the products will increase, and also since the two component parts are fixedly secured by welding, causing deformation of the products due to welding strain, it has been necessary to remove the welding strain throughout the whole welded joints.
While in the latter method of manufacturing a drive plate by forming a thin plate into a dish-shaped portion and a gear portion integrally, it is difficult to form gear teeth, and also it is difficult to form the thick-walled peripheral portion having a uniform thickness. Particularly, in the method of forming the thick-walled peripheral portion by spinning, it is difficult to obtain a wall thickness enough to form gear teeth.